Messages in this thread | | | Date | Thu, 15 Feb 2024 11:28:34 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling |
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On Wed, Feb 14, 2024 at 07:45:18PM -0800, Paul E. McKenney wrote: > On Wed, Feb 14, 2024 at 06:03:28PM -0800, Ankur Arora wrote: > > > > Paul E. McKenney <paulmck@kernel.org> writes: > > > > > On Mon, Feb 12, 2024 at 09:55:24PM -0800, Ankur Arora wrote: > > >> Hi, > > >> > > >> This series adds a new scheduling model PREEMPT_AUTO, which like > > >> PREEMPT_DYNAMIC allows dynamic switching between a none/voluntary/full > > >> preemption model. However, unlike PREEMPT_DYNAMIC, it doesn't depend > > >> on explicit preemption points for the voluntary models. > > >> > > >> The series is based on Thomas' original proposal which he outlined > > >> in [1], [2] and in his PoC [3]. > > >> > > >> An earlier RFC version is at [4]. > > > > > > This uncovered a couple of latent bugs in RCU due to its having been > > > a good long time since anyone built a !SMP preemptible kernel with > > > non-preemptible RCU. I have a couple of fixes queued on -rcu [1], most > > > likely for the merge window after next, but let me know if you need > > > them sooner. > > > > Thanks. As you can probably tell, I skipped out on !SMP in my testing. > > But, the attached diff should tide me over until the fixes are in. > > That was indeed my guess. ;-) > > > > I am also seeing OOM conditions during rcutorture testing of callback > > > flooding, but I am still looking into this. > > > > That's on the PREEMPT_AUTO && PREEMPT_VOLUNTARY configuration? > > On two of the PREEMPT_AUTO && PREEMPT_NONE configurations, but only on > two of them thus far. I am running a longer test to see if this might > be just luck. If not, I look to see what rcutorture scenarios TREE10 > and TRACE01 have in common.
And still TRACE01 and TREE10 are hitting OOMs, still not seeing what sets them apart. I also hit a grace-period hang in TREE04, which does CONFIG_PREEMPT_VOLUNTARY=y along with CONFIG_PREEMPT_AUTO=y. Something to dig into more.
I am also getting these from builds that enable KASAN:
vmlinux.o: warning: objtool: mwait_idle+0x13: call to tif_resched.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: acpi_processor_ffh_cstate_enter+0x36: call to tif_resched.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: cpu_idle_poll.isra.0+0x18: call to tif_resched.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: acpi_safe_halt+0x0: call to tif_resched.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: poll_idle+0x33: call to tif_resched.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: default_enter_idle+0x18: call to tif_resched.constprop.0() leaves .noinstr.text section
Does tif_resched() need to be marked noinstr or some such?
Tracing got harder to disable, but I beleive that is unrelated to lazy preemption. ;-)
Thanx, Paul
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